Off Flavors in Beer

Brewing is essentially a lesson in chemistry. What this means is that to get a perfect or neat perfect result, attention to detail must take place in the brewing process. There are many, many ways in which a beer can go wrong.

So what happens if a brewer’s attention lapses, or their knowledge base isn’t up to the task? Off flavors occur in the beer.

Now it should be noted that sometimes an off flavor is desired. I’ll note those when appropriate to do so.

Here is a list of flavors that indicate that something may have gone wrong.

Skunky
Symptoms: It smells like a skunk. Tastes like it as well.
Causes: Mercaptan created when Ultraviolet light isomerizes with the alpha acids in the beer. In other words, the beer interacted with light, hence the other term used for this off flavor – lightstruck.
Fixes: Only store beers in brown bottles, and keep out of the sun once poured. It only takes 20 minutes or so for a beer to go bad in the sun.
Ever Appropriate? No.

Diacetyl
Symptoms: Butter aroma or flavor. Small amounts come across as toffee, large amounts come across as butterscotch. Also leaves a slickness on the palate.
Causes:Incomplete fermentation; low temperature fermentation; Pediococcus (lactic Acid Bacteria; Long periods of wort cooling; underpitching of yeast.
Fixes:Allow for a full fermentation at a high temperature, as well as good sanitization habits should reduce the probability of this by a high amount.
Ever Appropriate? Yes. Scotch Ales, English Bitters, Dry stouts, Czech Pils, and Oktoberfests are all allowed to have this flavor.

Sour – Acetaldehyde
Symptoms: Tastes of grass or green apples. Strong vinegar or cider-like tastes
Causes: Premature removal from yeast; premature flocculation; to little oxygen for the yeast; bacterial spoilage; oxidation
Fixes: Full fermentation from a good yeast strain, and aeration of the wort will help prevent this.
Ever Appropriate? American Light Lagers, Standard Lagers, and Premium Lagers all allow for low levels of this. You can thank the folks of Budweiser for making this allowable.

Sour – Lactic Acid
Symptoms: Sour for sour’s sake. It’s a clean sour, not smelling like grass or apples. So if it tastes tart, but doesn’t smell like grass or apples, it’s probably lactic acid. There also might be a slight vinegar smell. Think white vinegar instead of cider vinegar.
Causes: Poor Sanitation; Acid Creating Bacteria; Some yeast strains; Excessive acid rest; Excessive mashing; storage of beer at warm temperature; Scratched fermenters (harder to clean, so more susceptible for Acid creating bacteria)
Fixes: Good Sanitation practices and using a different yeast strain is a good start. Shorter acid rests and mashing for less than two hours will also help.
Ever Appropriate? Good god yes. You’ve heard of Belgium right? Witbiers,Lambics and Flanders Ale all are perfect for lactic acid, as well as Berliner Weisse. Sourness is optional for American wheat or Rye beers, Dry Stouts, and Saisons.

Sweet
Symptoms: Tastes excessively sweet. Feels syrupy on the palate and sugary to the taste.
Causes: Low attenuation of the yeast strain; high temperature mash; addition of excessive sweet malts like dextrin or crystal malts; addition of lactose; poor yeast health
Fixes: Buy good yeast, reduce your grain composition to reduce the amount of sweeter malts, and ensure proper wort oxygenation should help you out.
Ever Appropriate? Yup. strong ales and lagers should be quite sweet. American light lagers and lambics should be slightly sweet.

Astringent
Symptoms: A puckering of the taste buds, with a possible unpleasant burn on the back of the throat.
Causes: To may tannins extracted from the grains. Overcrushing the grains, oversparging the mash, and a high pH balance of the water all lead to a perfect storm of astringency. Overhopping can cause this as well.
Fixes: Don’t overcrush the grain, use a low temperature sparge, and watch the pH levels of the water. Being concerned with sanitization couldn’t hurt either.
Ever Appropriate? Nope, Never.

Penolics
Symptoms: Smells and tastes like a band-aid, plastic or chloroseptic. Also smoke and/or clove taste or amoma is indicative of this.
Causes: Wild yeast; improper sanitation; the use of tap water; Using chlorine bleach as a sanitizer; some yeast and malt strains bring this; high pH water
Fixes: Use pure yeast strains, practice good sanitation, and use filtered water instead of tap, and you’ll go a long way to preventing this.
Ever Appropriate? Cloves and Smoke? yes. Band-aids, medicinal, or plastic? No. Cloves and smoke are appropriate for some Belgian beers, smoked beers, and some wheat beers.

Esters
Symptoms: Smells and tastes fruity, especially like banana, but pears, strawberries, apples, even citrus are sometimes symptoms.
Causes:Alcohols combining with acids at higher temperatures; some strains of yeast; higher fermentation temperatures.
Fixes: Choose a different yeast or lower your fermentation temperature.
Ever Appropriate?Yup. Ales, Doppelbocks, Eisbocks allow for this. American Dark Lager can have a small amount

Oxidized
Symptoms: Smells and tastes of paper, wet cardboard, or slight sherry.
Causes:Oxidative yeasts acting on higher alcoholic content beers create aldehydes.
Fixes: Use a different yeast strain, or lower the grist as to create less alcohol. You could also serve beer younger and/or ferment cooler.
Ever Appropriate? Oh yes. Hello barleywines. English Old Ales as well.

Musty
Symptoms: Smells and tastes like a damp basement, moss, or a wet garden.
Causes:Aeration of hot wort, or of beer during bottling.
Fixes: Prevent the aforementioned aeration when in wort or when bottling should nip this in the bud.
Ever Appropriate? Oddly enough, yes. Biere de Garde. Oh those wacky French.

Dimethyl Sulfide (DMS)
Symptoms: Vegetal tastes and aromas, particularly cooked corn, celery, and/or cabbage. Even shellfish like in higher amounts.
Causes: Poor sanitation; covered wort; not boiling the wort for at least an hour; contaminated yeast; over-sparging with water below 160 F; excessive cooling of the wort; underpitching the yeast
Fixes: Good Sanitation, and an open rolling boil for an hour or more should help with this. Fresh yeast and proper sparging will help as well.
Ever Appropriate? That Cream Ale you think smells like creamed corn? It’s supposed to smell that way.